Method and monitoring system for monitoring at least one subscriber line

ABSTRACT

The invention relates to a method for signaling a fault of at least one subscriber line to be monitored to a central facility and relates to a monitoring system for monitoring such a subscriber line. Up to now, it has been possible to continuously monitor ISDN base terminals. However, it bas been shown that not all messages and deactivations are logged in the switching center during the occurrence of a fault in an ISDN terminal. For this reason, the aim of the invention is to provide a method and monitoring system with which subscriber lines are permanently monitored and each fault message can be immediately reported to a central facility. To this end, at least one subscriber line to be monitored is firstly activated and is monitored by using a monitoring device ( 70, 72 ) that is looped in the U KO  interface ( 20, 22 ) of a corresponding connection line ( 30, 32 ). Afterwards, a connection to a central facility ( 120 ) is established via a separate subscriber line ( 110 ) in response to a fault, detected by the monitoring device, of the at least one subscriber line to be monitored. Lastly, fault messages and/or an item of information related to the subscriber line is/are transmitted to the central facility ( 120 ). The inventive method and system additionally permit the creation and evaluation of a D, B 1  or B 2  channel protocol from the central facility ( 120 ).

[0001] The present invention relates to a method for signaling a faultof at least one subscriber line to be monitored to a central facility aswell as to a monitoring system for monitoring such a subscriber line.

[0002] The acceptance of public telecommunications networks among thecustomers essentially depends on their reliability of operation andperformance. Therefore, a major task of the network operators is tomonitor established connections or connections to be established withinthese telecommunications networks and, if necessary, to perform a faultdiagnosis.

[0003] One possibility of monitoring ISDN telecommunications networks isto measure and log ISDN basic accesses at the S₀ interface at thetelephone subscriber end (see, for example, the operating instructionsof the ISDN S₀ basic access measuring and testing device Pegasus fromthe Festo Didactic KG company, Esslingen, as of 02/95; page 85).

[0004] German Patent DE 197 29027 describes a method for measuring orlogging an ISDN basic access which can also be executed independently ofthe telephone subscriber to be monitored. This is achieved by openingthe U_(K0) interface at a point of the connection line that isconvenient for measurement or logging. In the opened U_(K0) interface,the line signals are converted into IOM signals, and the IOM signals arein turn converted into S₀ frames. Consequently, all data of the tappedS₀ interface are available to already existing S₀ measuring devices atthe point where the connection line is opened.

[0005] The object of the present invention is now to provide a methodand a monitoring system with which at least one subscriber line can becontinuously monitored and with which a central security facility can beimmediately alerted in case of a fault.

[0006] This object of the present invention is achieved, first of all,by the method steps of claim 1.

[0007] According to that, a method is provided for signaling a fault ofat least one subscriber line to be monitored to a central facility, theat least one subscriber line being connected to a switching center via aconnection line which features a U_(K0) interface. In order to be ableto monitor the subscriber line, the switching center keeps thesubscriber line permanently active, i.e., in the rest state,predetermined test messages (keep alive, polling) are continuouslytransmitted from the switching center to the subscriber line and viceversa, for example, every ten seconds, so that an interruption of theconnection line can always be detected in this manner. The permanentactivation can also refer to layer 1, i.e., the synchronization of theU_(K0) interface can be used for monitoring. A monitoring device, whichis looped into the U_(K0) interface of the corresponding connectionline, monitors the at least one subscriber line. This is done, forexample, by checking the test messages, which are transmitted during theactivation, for their presence on the connection line. If the monitoringdevice detects a fault of the at least one subscriber line to bemonitored, for example, an interruption of the connection line, aconnection to the central facility is established via a separatesubscriber line, in particular, of a public telecommunications network.Subsequently, a fault message and/or an item of information related tothe subscriber line, such as the address or call number o f thedisturbed subscriber line, is/are transmitted to the central facility.

[0008] In this manner, it is possible to continuously monitor asubscriber line and to transmit a fault message and the address of thedisturbed subscriber line to a central security facility in case of afault.

[0009] Advantageous refinements are the subject matter of the subclaims.

[0010] The monitoring device is expediently looped into the U_(K0)interface of the respective connection line near the switching center,i.e., in the same building.

[0011] If the intention is to use the method to monitor a plurality ofsubscriber lines assigned to the switching center and to measure and/orlog their states in case of a fault, initially, a first connectionset-up is initiated at this or another external terminal device via theseparate subscriber line preferably to a DTMF (multifrequency dialing)controllable switching matrix, subsequent to the transmission of thefault message and/or of the item of information related to thesubscriber line to the central facility. Thereupon, the switching matrixis programmed as a function of the item of information related to thesubscriber line in such a manner that a measuring device, which isconnected to the separate subscriber line, can be connected to thedisturbed subscriber line via a U_(K0) tap of the respective subscriberline that is contained in the monitoring device. Subsequently, theconnection is released again. After that, a second connection set-up isinitiated at the central facility or at the other external terminaldevice via the separate subscriber line to the measuring device, whichis now caused to measure and/or log the state of the disturbedsubscriber line and to transmit the results via the existing connectionto the central facility or to the external terminal device.

[0012] Preferably, the subscriber lines to be monitored and the separatesubscriber line are ISDN basic accesses. In this case, the measuringdevice is designed to create a D channel protocol of the S₀ interface ofthe ISDN basic access. To this end, however, it is required to connecteach connection line to the switching matrix via the U_(K0) tap. The UKOtap of each monitoring device provides that the data tapped at theU_(K0) interface of the connection line is converted into an S₀ framewhich can be processed by the measuring device. Such a U_(K0) tap isknown from German Patent DE 197 29072.

[0013] This object of the present invention is achieved, secondly, bythe features of claim 7.

[0014] According to that, provision is made for a monitoring system formonitoring at least one subscriber line which is connected to aswitching center via a connection line which features a U_(K0)interface. Looped into the U_(K0) interface of each connection line tobe monitored that is connected to the switching center is moreover adevice for monitoring the associated subscriber line. Each monitoringdevice is connectable to a device for generating a fault message and/oran item of information related to the subscriber line, the latterdevice, in turn, being connected to a separate subscriber line. Via thisseparate subscriber line, it is possible for the device for generating afault message and/or an item of information related to the subscriberline to establish a connection to a central facility to transmit thefault message and/or the item of information related to the subscriberline. The device for generating a fault message and/or an item ofinformation related to the subscriber line can be, for example, a DS7500 device from the effeff company.

[0015] Except for the central facility, all devices and units can beaccommodated in the building of the switching center.

[0016] Advantageous refinements are the subject matter of the subclaims.

[0017] Advantageously, each monitoring device has a detector as well asa controllable switch which, when the detector detects a fault of theassociated subscriber line, connects the respective monitoring device tothe device for generating a fault message and/or an item of informationrelated to the subscriber line. In this manner, the device forgenerating a fault message and/or an item of information related to thesubscriber line is caused to generate the fault message and/or the itemof information related to the subscriber line about the disturbedsubscriber line and to transmit it to the central facility.

[0018] In order to be able to measure and/or log at least one subscriberline, at least one monitoring device is connectable to a measuringdevice which is connected to the separate subscriber line. Thus, it ispossible for the measuring device to measure and/or log the state of thedisturbed subscriber connection, which is tapped via the monitoringdevice, and to transmit the results via a public network to the centralfacility or to another external device.

[0019] To permit monitoring of a plurality of subscriber lines, aswitching matrix is connected between the monitoring devices and themeasuring device. Moreover, a DTMF remote control device is connected tothe separate subscriber line and to the switching matrix, the DTMFremote control device being able to be dialed up by the central facilityor another external device via the separate subscriber line forcontrolling the switching matrix.

[0020] If the item of information related to the subscriber lineincludes the address of a disturbed subscriber line, then the switchingmatrix can be programmed via the DTMF control device as a function ofthe address in such a manner that the measuring device can be connectedto the corresponding U_(K0) tap.

[0021] If the subscriber lines are ISDN basic accesses, each monitoringdevice features a U_(K0) tap, the S₀ interface of the monitoring devicebeing connected to the switching matrix. In this manner, the tapped S₀interface of the disturbed ISDN basic access can be tapped via theswitching matrix and connected to the measuring device. The measuringdevice is capable of analyzing the D, B, or B₂ channels of an ISDNconnection.

[0022] Furthermore, it should be mentioned that, besides the ISDNconnections mentioned here, it is also possible to monitor standardfixed lines and direct data connections which are provided with a U_(K0)interface.

[0023] In the following, the present invention will be explained ingreater detail in the light of an exemplary embodiment in conjunctionwith the attached drawing.

[0024] The only figure shows a monitoring system which is universallydenoted by 10 and is connected near a digital transmission center 40 viaa monitoring device 70 at an opened U_(K0) interface 20 of a connectionline 30 and via a monitoring device 72 at an opened U_(K0) interface 22of a connection line 32. Although only two connection lines areconnected to digital switching center 40, it is obvious that a pluralityof connection lines can be connected to digital switching center 40 andto monitoring system 10.

[0025] At the subscriber end, connection lines 20 and 22 are terminatedat the ISDN basic access with a network termination device 50 and 52,respectively. Each network termination device 50, 52 is connected to anISDN telephone 60 or 62, respectively. At this point, it should bementioned that monitoring system 10 can be suitable not only formonitoring connection lines featuring ISDN basic accesses but also formonitoring standard fixed lines and direct data connections.

[0026] Monitoring devices 70 and 72 each contain detectors (not shown)with which, for example, an interruption on respective connection line30 or 32 can be detected as a fault. Moreover, each monitoring device70, 72 features a potential-free contact 80 and 82, respectively, viawhich a fault of the associated subscriber line that is detected by thecorresponding monitoring device (70, 72) can be signaled to a device forgenerating a fault message and/or an item of information related to thesubscriber line 150, in short called signaling device hereinafter.Moreover, each monitoring device 70, 72 has a U_(K0) tap (not shown),which is known per se and via which the monitoring devices can beconnected to a switching matrix 90. The mode of operation of the U_(K0)tap is known from German Patent DE 197 29027, which is included hereinby reference. The U_(K0) taps provide that the signals to be tapped atU_(K0) interfaces 20 and 22 are converted into S₀ frames which, in turn,can be processed in a conventional S₀ measuring device 100, which isconnected to switching matrix 90. As will still be explained in greaterdetail below, the state of each ISDN basic access, in particular, the Dchannel of an ISDN connection, can be measured and logged usingmeasuring device 100. Moreover, measuring device 100 is connected to anISDN basic access 110 via which a connection can be established via apublic network to a central facility 120 or to an arbitrary terminaldevice equipped with an ISDN card. In this manner, as will still beexplained in greater detail below, it is possible to transmit themeasuring results and logs of measuring device 100 to central facility120.

[0027] Also connected to ISDN basic access 110 is, for example, a DTMFremote control device 130, possibly via a conventional terminal adapter140.

[0028] On the output side, DTMF remote control device 130 is connectedto switching matrix 90. The control of switching matrix 90 through DTMFremote control device 130 can take place, for example, via centralfacility 120. For that purpose, the central facility must be able togenerate signals according to the multifrequency dialing method. Amethod, which is suitable for this, is disclosed in German Patent 199 34622, which is also included herein by reference.

[0029] In the following, the mode of operation of monitoring system 10will be explained in greater detail. First of all, the two ISDN basicaccesses of connection lines 30 and 32 are assumed to be continuouslymonitored with the aid of a permanent activation. Due to the triggeredpermanent activation, predetermined test messages are transmitted backand forth between digital switching center 40 and ISDN telephones 60 and62 approximately every ten seconds, also in the rest state. As long asthe detectors of monitoring devices 70 and 72 detect the presence ofthese test messages, monitoring system 10 is in the so-called“monitoring mode”. However, as soon as no test messages are detected anymore on one of connection lines 30 or 32, i.e., an interruption of theconnection line is detected, monitoring system 10 goes into thesignaling and measuring mode with respect to this connection line. Inthis context, it is assumed, for example, that connection line 30 hasbeen interrupted. In response to the interruption of connection line 30,the detector of monitoring device 70 closes potential-free contact 80,as a result of which a fault of the ISDN basic access of connection line30 is signaled to signaling device 150. Signaling device 150 recognizesthe disturbed ISDN basic access and the call number thereof from theactuation of potential-free contact 80. Thereupon, signaling device 150establishes a connection, via ISDN basic access 110, to central facility120 and transmits a corresponding fault message as well as the callnumber of the disturbed ISDN basic access to central facility 120. Theconnection between signaling device 150 and central facility 120 can bereleased after the transmission of the fault message and the callnumber. Now, a monitoring person at central facility 120 initiates aconnection set-up via ISDN basic access 110 to DTMF remote controldevice 130 and enters the call number of the disturbed ISDN basic accessat central facility 120, the call number being transmitted to DTMFremote control device 130 by multifrequency tones. In response to thereceived call number of the disturbed ISDN basic access, DTMF remotecontrol device 130 controls switching matrix 90 in such a manner thatmeasuring device 100 is able to measure and/or log the correspondingsubscriber line via the U_(K0) tap. Subsequently, the monitoring personreleases the connection to DTMF remote control device 130 again, andinitiates a second connection set-up via ISDN basic access 110 tomeasuring device 100. Measuring device 100 is now connected to theU_(K0) tap of the corresponding monitoring device (70, 72) and isconsequently able to analyze and log the D, B₁ or B₂ channels of thedisturbed ISDN basic access. The current states, results and logs of thedisturbed ISDN basic access can be transmitted by measuring device 100via ISDN basic access 110 to central facility 120 and there be displayedby the monitoring person on a display. In this manner, the monitoringperson can immediately decide whether it is required to send a servicetechnician to the customer of the disturbed ISDN basic access or whetherremote maintenance is possible. After the fault has been eliminated,monitoring system 10 is reset to the monitoring mode with respect toconnection line 30, that is, potential-free contact 80 of monitoringdevice 70 is opened again.

[0030] Although in the present example, only a measuring device 100 isconnected to switching matrix 90 and only one ISDN basic access 110 isused, it is conceivable to connect a plurality of measuring devices 100to switching matrix 90 and to connect the measuring devices to centralfacility 120 via a plurality of ISDN basic accesses.

[0031] Thanks to the described monitoring system 10, it is possible tocontinuously monitor one or a plurality of subscriber line(s) and totransmit a fault message and the address of the disturbed subscriberline to a central facility in case of a fault. Moreover, it is possibleto directly influence the monitoring system in many ways from thecentral facility via the public network. For instance, it is conceivablefor call forwarding to be activated in switching center 40 for adisturbed ISDN basic access.

[0032] List of Reference Symbols

[0033]10 monitoring system

[0034]20, 22 U_(K0) interface

[0035]30, 32 connection line

[0036]40 digital switching center

[0037]50, 52 network termination device

[0038]60, 62 ISDN telephone

[0039]70, 72 monitoring device

[0040]80, 82 potential-free contact

[0041]90 switching matrix

[0042]100 S₀ measuring device

[0043]110 ISDN basic access

[0044]120 central facility

[0045]130 DTMF remote control device

[0046]140 terminal adapter

[0047]150 device for generating a fault message and/or an item ofinformation related to the subscriber line, signaling device

What is claimed is:
 1. A method for signaling a fault of at least onesubscriber line to be monitored to a central facility (120), the atleast one subscriber line being connected to a switching center (40) viaa connection line (30, 32) which features a U_(K0) interface (20, 22),comprising the following method steps: permanent activation, from theswitching center, of the at least one subscriber line to be monitored;monitoring of the at least one subscriber line using a monitoring device(70, 72), which is looped into the U_(K0) interface (20, 22) of thecorresponding connection line (30, 32); establishing a connection to thecentral facility (120) via a separate subscriber line (110) in responseto a fault, detected by the device, of the at least one subscriber lineto be monitored; and transmitting a fault message and/or an item ofinformation related to the subscriber line to the central facility. 2.The method as recited in claim 1, wherein the monitoring device (70, 72)is looped into the U_(K0) interface (20, 22) of the correspondingconnection line (30, 32) near the switching center (40);
 3. The methodas recited in claim 1 or 2, characterized by the following steps:initiation of a first connection set-up at the central facility (120) orto another external terminal device via the separate subscriber line(110) to a controllable switching matrix (90), subsequent to thetransmission of the fault message and/or of the item of informationrelated to the subscriber line to the central facility; programming ofthe switching matrix (90) as a function of the item of informationrelated to the subscriber line in such a manner that a measuring device(100), which is connected to the separate subscriber line (110), can beconnected to the monitoring device (70, 72) of the correspondingconnection line (30, 32); release of the connection; and initiation of asecond connection set-up at the central facility (120) or of anotherexternal terminal device via the separate subscriber line (110) to themeasuring device (100), which is able to measure and/or log the state ofthe disturbed subscriber line and to transmit it to the central facilityor to the other external device.
 4. The method as recited in one of theclaims 1 through 3, wherein the at least one subscriber line to bemonitored and the separate subscriber line are each an ISDN basicaccess.
 5. The method as recited in claim 4, wherein the measuringdevice (100) is able to create a D, B₁ or B₂ channel protocol; and eachconnection line (30, 32) is connected to the switching matrix (90) via aU_(K0) tap contained in the monitoring device (70, 72).
 6. A monitoringsystem for monitoring at least one subscriber line which is connected toa switching center (40) via a connection line (30, 32) which features aU_(K0) interface (20, 22), a device (70, 72) for monitoring a subscriberline connected thereto being looped into the U_(K0) interface (20, 22)of each connection line (30, 32), which is connected to the switchingcenter (40) and to which a subscriber line to be monitored is connected,each monitoring device (70, 72) being connectable to a device forgenerating (150) a fault message and/or an item of information relatedto the subscriber line, and the device (150) for generating a faultmessage and/or an item of information related to the subscriber line isconnected to a separate subscriber line (110) via which this device canestablish a connection to a central facility (120) to transmit the faultmessage and/or the item of information related to the subscriber line tothe central facility.
 7. The monitoring system as recited in claim 6,wherein each monitoring device (70, 72) has a detector as well as acontrollable switch (80, 82) which, when the detector of the respectivemonitoring device (70, 72) detects a fault of the associated subscriberline, signals the detected fault to the device (150) for generating afault message and/or an item of information related to the subscriberline.
 8. The monitoring system as recited in claim 6 or 7, wherein atleast one monitoring device (70, 72) is connectable to a measuringdevice (100), which is connected to the separate subscriber line (110)and able to measure and/or log the state of the disturbed subscriberline that is associated with the monitoring device (70, 72) and totransmit it to the central facility (120) or to another external device.9. The monitoring system as recited in claim 8, wherein a switchingmatrix (90) is connected between the monitoring devices (70, 72) and themeasuring device (100); a remote control device (130) is connected tothe separate subscriber line (110) and to the switching matrix (90), theremote control device (130) being able to be dialed up by the centralfacility (120) or by another external device via the separate subscriberline (110) for controlling the switching matrix (90).
 10. The monitoringsystem as recited in claim 9, wherein the item of information related tothe subscriber line includes the address of a disturbed subscriber line;and the switching matrix (90) is programmed via the control device (130)as a function of the address in such a manner that the measuring device(100) can be connected to the corresponding monitoring device (70, 72).11. The monitoring system as recited in one of the claims 6 through 10,wherein the subscriber lines are ISDN basic accesses, each monitoringdevice (70, 72) features a U_(K0) tap, the S₀ interface being connectedto the switching matrix (90); and the measuring device (100) is designedto analyze the D, B₁ or B₂ channel of an ISDN connection.